The present invention relates to a valve assembly used for coupling a catheter to a cannula to provide a pathway for introducing the catheter into internal arteries, organs, or cavities.
Such coupling or luer connectors are widely used for controlling the introduction of medications or instruments into the human body. It is imperative in medical applications that a dependable, inexpensive and fluid-tight valve be provided for this purpose.
A prior art device used for providing a fluid-tight pathway for the introduction of catheters is illustrated in FIG. 1.
A central housing 10 normally comprised of plastic, has a port cavity 11 at one end for retaining a four element system for sealing a catheter extending along the pathway 38. A duck bill 32 has a slit at the lower end which opens when the catheter is inserted. The one-way valve or "duck bill" 32 is used to prevent the leakage or flashback of blood or fluid from the inner cavity 44 into the port cavity 11 when the catheter is removed from pathway 38. The slit on the duck bill 32 generally does not form a fluid-tight seal about the catheter. A flexible plastic tube 28 inserted between two washers 26 and 30 is used to form a fluid seal about a catheter guidewire or other intravenous instruments introduced via a cannula.
The seal 28 operates by deforming under pressure applied by screwing a cap 12 with threads 14 onto the housing threads 24 such that the annular surface 42 compresses the seal 28. The inner surface of seal tube 28 deforms against the outer wall of a catheter positioned along path 38 to form a fluid-tight seal.
When the cap 12 is unscrewed from the housing 10, it is retained on the end of the housing by a pair of rings 18 and 22. Ring 18 protrudes outwardly from the inner cylinder 41 that supports the annular compression surface 42. Ring 22 protrudes inwardly from the surface 20 of the housing at the open end of cavity 11. The cap 12 snaps onto the housing 10 by manually pushing ring 18 through the hole defined by ring 22.
The rings 18 and 22 for retaining the cap 12 on the housing have permitted the easy removal of the cap. The application of 3-5 lbs. of pressure to the cap 12 has been sufficient to remove it from the housing 10. As a result, the cap is easily removed and misplaced resulting in the inability to properly seal the pathway 38. This results in the necessity of replacing the valve, or worse, it can endanger the patient if the valve continues to be used.
The failure to form a seal about the catheter or to close the pathway 38 after removal of the catheter can result in the entrainment of air into the blood stream. The intravascular entrainment of air can occur with very minor negative pressures, yet can lead to hypotension and hypoxia within the patient under treatment. If air entrainment is rapid enough, an acute fall in arterial and pulmonary artery pressures can occur.
The cap 12 can also be tightened to the point of causing the collapse of one or more lumens within the catheter and thereby slowing or stopping the flow of fluid therein. As a result, introducer valves which are used frequently during operative and post-operative procedures and which have any undetected blockage within catheter lumens can have deleterious consequences.
The cap 12 has generally been made from a rigid PVC material. The cap is formed on a mold and then cooled before it is removed from the mold to avoid deformation.